Field of the Invention
The invention relates to a device for distributing gases in liquids, comprising: an aerating element made of plastic, with an upper side and a lower side joined with the upper side, a support element, and a gas inlet, wherein the aerating element comprises at least one cavity that can be filled with gas through the gas inlet, wherein at least the area of the upper side of the aerating element comprises holes, perforations or the like as the gas outlet, and wherein the support element is situated in the cavity of the aerating element.
Description of Related Art
The progression of many biological or chemical processes is also determined among other factors by the gas content of the liquids involved in the processes. The solubility of gases in liquid depends on several parameters, for example the temperature and pressure. For this reason, the gas content of liquids can be influenced and varied until a saturation limit has been reached. Different solutions are known for this purpose. Some of these solutions relate to distributing gases in liquids to increase the gas content of the liquid. For example, a higher oxygen content in the water is desired in fish farming or purification plants, to which end the basins are aerated. When aerating liquids, an attempt is generally made to generate especially numerous, small air bubbles, and distribute the latter uniformly in the liquid, since as a result the boundary surface between air and water is larger than given a few large air bubbles, and the air can dissolve especially well in the water (diffusion).
Various solutions are known for distributing gases in liquids, in particular for aerating liquids. For example, a flat aerating mat made out of plastic is known from WO 2007/051150 A2. The aerating mat consists of a perforated upper film and a lower film, which are joined with each other in an adhesive bonding or welding process in such a way that several oblong cavities or chambers form between the upper film and lower film. Apart from the perforation, the aerating mat thus exhibits similarities to an air mattress. In order to aerate liquids, the aerating mat can be stretched out in a frame, for example one placed on the bottom of a water basin. The flat design of the aerating mats makes it possible to achieve a uniform bubble distribution. Several aerating mats placed back-to-back and side-by-side can be used to aerate larger surfaces.
The disadvantage to aerating mats known from WO 2007/051150 A2 is that the adhesively bonded or welded seams represent weak points. Since the upper film must expand to open the holes, the danger becomes that the aerating mat will be unable to withstand the high internal pressure in the area of the welded joints or seams. In particular, cracks may form in proximity to the welded seams, since the films strongly expand in this region, while almost no expansion can take place in the area of the welded seam itself. As a consequence, the film tears in the area of the welded joints or seams, and the aerating mat fails. Another disadvantage lies in the fact that such aerating mats are complicated and expensive to manufacture, for example since ultrasound or high-frequency welding devices must be used for welding together the upper film and lower film.
Also known for aerating liquids are so-called “tube aerators”, for example those described in DE 20 2006 004 514 U1. Involved here is a flexible, perforated plastic hose that is slipped over a cylindrical tube serving as the support tube. The circumference of the perforated hose is only slightly larger than the circumference of the support tube, so that the perforated hose wall tightly abuts against the support tube. The perforated hose is sealed off from the support tube at both ends. Air can be supplied from inside by way of a line or hose via an opening provided in the support tube, so that the perforated hose is lifted from the support tube and expands. The air can exit the numerous small holes in the flexible hose in the form of small bubbles.
Known tube aerators have the disadvantage of a bubble distribution unsuitable for aerating larger surfaces. The cylindrical shape of the support tube and flexible hose do offer the advantage of uniformly expanding when exposed to pressure. However, one disadvantage to circular cross sections is that the air exits the hose in a radial direction, causing a portion of the air to also exit toward the bottom and side. As a result, circular cross sections cannot be used to uniformly distribute the bubbles over a flat surface, for example over the bottom of a water basin. Another disadvantage to tube aerators with cylindrical support tubes lies in the fact that the support tube exhibits a cavity. The air present in the cavity generates buoyancy, thereby hampering the assembly of tube aerators underwater. In order to balance out this disadvantage, the cavities are often filled with concrete, sand or the like. However, this leads to another disadvantage, since the filling makes it more complicated and expensive to manufacture and transport the tube aerators. Finally, another disadvantage of tube aerators involves the intricate piping. Each individual tube aerator must have its own air connection, and thus is only clamped on one side. In addition, tube aerators often have very high buoyant forces (with the cavity not filled) or very high downforces (e.g., when filled with concrete). In combination with the unilateral clamping, both lead to very high torque loads, so that very stable, and hence very expensive, piping must be installed.